package com.mask.chapter01;

import java.util.HashMap;
import java.util.Scanner;

public class Test3 {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        String str = sc.next();
        HashMap<Character,Integer> map = new HashMap <>();
        for(int i=0;i<str.length() ;i++) {
            char ch = str.charAt(i);
            if(map.get(ch) == null)
                map.put(ch, 1);
            else
                map.put(ch, map.get(ch).intValue()+1);
        }
        System.out.println(map.get('a'));    //判断字符'a'出现的次数
    }
}